Identification Of QTL Related With Nitrogen Utilization Using Chromosome Single Segment Substituted Lines In Rice Seedling

Rice is one of the major grain crops in China,and in a social environment where there will be no major change in the area planted in China,by increasing the yield of rice,it becomes the basic way to keep increasing the yield of grain every year and the powerful guarantee to ensure the national food security.Nitrogen is one of the most important factors that restrict the growth and development of rice and affect the yield of rice,therefore,the study of nitrogen use related traits in rice is of great significance for rice genetic improvement.In this study,a set of Chromosome Segment Substitution Lines(CSSLs)was constructed using Japonica rice variety Nipponbare as the donor parent and Indica rice variety Guangluai 4 as the recurrent parent,plant height(PH),root dry weight(RDW),seedling dry weight(SDW),plant dry weight(PDW),nitrogen use efficiency(NUE)and nitrogen accumulation(NA)were used as six traits to identify QTL related to nitrogen use under high nitrogen(HN)and low nitrogen(LN)conditions,mapping QTL for nitrogen use and related traits in rice seedling stage.The main results were as follows:1.Phenotypic analysis of plant height(PH),root dry weight(RDW),seedling dry weight(SDW),plant dry weight(PDW)and nitrogen use efficiency(NUE)and nitrogen accumulation(NA)of chromosome segment substitution lines and their parents(table 1),the plant height(PH),seedling dry weight(SDW),plant dry weight(PDW)and nitrogen use efficiency(NUE)and nitrogen accumulation(NA)of parents(Japonica Rice variety Nipponbare and indica rice variety Guangluai 4)and the population of chromosome segment substitution lines under low nitrogen(LN)conditions were lower than those under high nitrogen(HN)conditions,and the root dry weight increases.The results showed that rice seedlings under low nitrogen(LN)conditions could induce root system to inhibit the growth of shoot and leaf,and the responses of Guanglui and Japonia were consistent with those of their parents under low nitrogen(LN)conditions According to the Chromosome Segment Substitution Lines(CSSLs)population,each trait value showed continuous normal distribution and two-way overparent separation,which showed quantitative traits,which indicated that these traits met the requirements of QTL mapping.2.The correlation analysis of rice seedling traits under high nitrogen(HN)and low nitrogen(LN)showed that plant Height(PH),root dry weight(RDW),seedling dry weight(SDW)and nitrogen accumulation(NA)were significantly correlated with each other at seedling stage,the results showed that the growth and development of rice seedling was the result of the cooperation of the root system of rice underground and the stem and leaf of rice above ground.The Correlation Coefficient between Plant Height(PH)and root stem mass(RDW)under low nitrogen(LN)condition was the smallest(0.211),the Correlation Coefficient between RDW under low nitrogen condition(LN)and RDW under high nitrogen condition(HN)was the largest(0.924).3.A total of 35 QTL for plant height(PH),root dry weight(RDW),seedling dry weight(SDW),total dry weight(PD W),nitrogen use efficiency(NUE),nitrogen accumulation(NA)and their relative traits were detected under high and low nitrogen conditions,among them,13 QTL were detected under high nitrogen(HN)condition,10 QTL under low nitrogen(LN)condition and 12 QTL under low and high nitrogen(LN/HN)condition relative traits.Two regions containing multiple qtls with different nitrogen levels and their relative traits were detected as hot spots of qtls.The hot spots of QTL detected near the end of the long arm of Chromosome 1 and the hot spots of qtls previously reported are near the same chromosome region,however,the hot spots of QTL detected at the end of the short arm of Chromosome 1 have not been reported.These results will provide the basis for breeding rice varieties with high nitrogen use efficiency at seedling stage by molecular marker-assisted selection.